This invention relates to a structural member of the type used to form a supporting framework for an airship.
In the field of aviation, particularly in rigid and semirigid airships, as well as also in the field of structural engineering, light-weight structural members are required as structural elements for large-volume framework constructions. In order to accommodate the large pressure loads, which can occur in such constructions, structural members used for this purpose usually consist of three parallel longitudinal chords, with struts disposed diagonally therebetween, connecting the three longitudinal chords with one another at nodal points, to create an elongated polygonal structure, which is used in turn to form longitudinal beams and transverse spars of the supporting framework for an airship.
For example, German patent document DE-PS 520664 discloses a structural member having three longitudinal chords, with struts arranged therebetween. The longitudinal chords consist of three profiles with an inwardly open cross-section, between which strut devices are arranged which have two chord devices, which are each connected to different cross-section sides of the longitudinal profile. Connections between the longitudinal profiles and the strut device are made by rivets. The longitudinal profiles and the transverse struts are made of especially shaped parts, and must have flanges in order to be able to carry out the riveted connection. However, even in the case of a simple arrangement of this type, the construction is cumbersome and time-consuming so that certain, construction-related sizes and weights cannot be avoided.
In German patent document DE-PS 610976, a support construction for airships is described in which achieves a corner profile reinforcement relative to earlier constructions, without any increase in weight. For this purpose, additional construction strips made of sheet metal are provided which are not curved in their center part but are essentially planar, and are arranged such that they connect the corner profile edges with one another in a chord-type manner.
Such a planar construction strip prevents bending-out to any side. The weight of the strips is reduced by means of holes and recesses and the strips are kept narrower by beaded flanges which, in turn, saves more weight.
The node points for the support which are joined in this manner must not fall below a certain size and weight, because the introduction of force at the node points presents problems. patent document GB-PS 123604, discloses a support construction which uses parallelogram-type elastic frames formed of a laminated material. Such frames are arranged next to one another in a certain sequence in the longitudinal direction between the supporting spars, and are fastened on the support. The frames are fastened to one another and to the chords by gluing or pasting. By means of this arrangement, the stiffness of the keel (support) is improved, without an increase in weight.
German patent document DE-PS 657909 describes a tube-shaped light-weight material component consisting of cellulosics, or paper or fiber materials impregnated or perfused with such cellulosics. Several such tubes, can be joined and glued together to form bundles, by means of a free solvent or a solvent interspersed with cellulosics. These bundles may also easily be sheathed by means of an enveloping shell made of the above-mentioned fiber materials, such as a paper web. In this patent, a special embodiment is described in which two tubes are arranged at a right angle to form a T-piece, and are glued together by means of a solvent to form a unit. Additional information concerning this type of a T-shaped arrangement (that is, the construction of a simple node) is not found in this patent document. When a tube-shaped component is pushed into one of the openings of the T-piece, an internal adhesive which may be required for the assembly is damaged in the area of the overlapping of the pushed-in components, and a secure glued connection of the components, which is absolutely necessary, is not achieved. support construction is found in Swiss patent document CH-PS 49 829, in which a support is composed of smaller, four-cornered or rectangular frames. By joining the frames in the longitudinal direction, a support or keel for receiving the gondola, etc. is provided in the longitudinal direction of the airship. Adjacent frames fitted together in this manner are connected and reinforced by diagonal tension wires so that a uniform rigid support is obtained.
The tube-shaped extensions on the frames, which are provided to join the frames, in this case, are pushed into the extensions and connections of the adjoining frame. However, this design has the above-mentioned serious disadvantage; specifically that a possibly required adhesive in the area of the pushed-together extension is not reliably effective and distributed in a uniform manner. Thus, when considered as a whole, the stability of this nodal point is unsafe.
When assessing the state of the art known on the basis of the above-mentioned patent documents, it is noted that each of the constructions indicated as an example has considerable defects.
It is demonstrated that a problem exists in that the tubes which are to be used are highly loadable, but are also locally very sensitive with respect to the introduction of force. These tubes are produced from highly stressable materials, together with bracing parts made of a corresponding material. Maximal can be borne by using such a highly stressable construction material (for example, by means of chemical-fiber-reinforced tubes) only if the nodal connections also introduce force into the structural member optimally at every point. Thus, special attention must be paid to the nodal connection: not only to the specific material for the node parts, but also to provide a design which achieves an optimal introduction of force into the support.
The disadvantages found in the prior art are mainly that
a) despite the selection of highly stressable materials, the high stability provided by these materials cannot be completely utilized; PA1 b) the introduction of force into the support takes place non-uniformly and, as a result, premature failure is possible; PA1 c) the adhesive connection cannot be tested with respect to a complete and uniform glued connection; PA1 d) a large scattering of the stability values results in considerable difficulties, and, during the development and construction of nodal points, no reliable values and guarantees can be supplied; and PA1 e) the manufacturing is not economical. is an object of the present invention to eliminate the above-mentioned disadvantages of the previous state of the art, and to provide a nodal connection for supports in which the stability characteristics of the support and of the strut can be fully utilized, and in which forces are distributed within the structural member in an optimal manner.
This object is achieved in a structural member with longitudinal chords and struts which are connected with one another at respective nodal points, by the nodal point configuration according to the invention, which consists of at least one base shell having trough shaped longitudinal channels for receiving the longitudinal chord and the transverse struts, and at least one closure shell which, together with the at least one base shell, completes a sleeve-type enclosure of the longitudinal chord and the transverse strut together with the base shell, in a form-locking fashion.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.